1. Field of the Invention
The present invention relates to a damping or dampening unit for offset printing presses, the damping unit having a tipping roller which is immersed in a damping solution pan, a metering roller associated with the tipping roller, and a form roller which applies the damping solution to a printing plate of a plate cylinder. The rollers of the damping unit can be driven at different speeds and in different directions.
2. Background Information
To achieve a uniform film of damping solution with known damping units, (i.e. German Patent No. 91 10 345 U1), the respective rollers can be driven at different circumferential speeds or even in different directions so that the outer surfaces of the respective rollers may exhibit opposing directions of motion at the lines of contact. All of these measures can serve to minimize the amount of damping solution applied to prevent excess damping of the printing plate. The problem with these rollers, some of which are frictionally driven, is that the rotation of the printing plate can be transferred to the individual rollers. At higher press speeds, this can result in the application of additional driving force to slower moving rollers, making the precise metering of damping solution more difficult.